The invention relates to a device for penetratingly extending a blind hole introduced into hard tissue, particularly a jawbone.
Such extension of a bone bore is required, for example, in the field of dental surgery wherein performing a procedure referred to as “sinus lift”. Sinus lift refers to a surgical procedure where the sinus mucous membrane is a partially detached from the jawbone and lifted to provide space between the bone and the sinus mucous membrane. Autologous bone (e.g., from tuber maxillae, linea obliqua, the chin region or from the iliac crest (bone replacement materials, bone chips)) or a synthetic bone replacement material (for example bone replacement material with the brand name Bio-Oss from the company Geistlich AG), frequently mixed with autologous bone, is introduced in the generated cavity. This material should transform itself into bone within six months so as to ensure a solid foundation for an implant.
The conventional approach with a sinus lift is to prepare a buccal mucoperiosteal flap in the molar region and to mill an oval window in the exposed bone without damaging the underlying sinus mucous membrane. The oval bone disk suspended from the sinus mucous membrane is then carefully pressed towards the maxillary antrum, while the sinus mucous membrane is simultaneously carefully detached from the bone around the window with special instruments. Because the sinus mucous membrane is very delicate, somewhat comparable to the skin of an egg, this process must be performed very carefully because of the risk of damage to the sinus mucous membrane. The cavity generated in this way in the maxillary antrum is now filled through the window with the bone replacement material and the buccal window is covered with a foil. The foil is typically made from a resorbable material, for example a membrane with the brand name Bio-Guide from the company Geistlich AG. The mucoperiosteal flap is then tightly stitched. The method is quite invasive and stresses the patient due to severe swelling and discoloration for up to 10 days, eventually also due to pain.
This surgical method is frequently also referred to as “open” or “classic” sinus lift. If sufficient residual bone height exists (approximately with the height of 5 mm), then implants can be inserted “simultaneously” with the sinus lift (one-time sinus lift). The implant can only be fully loaded after the bone replacement material has solidified. If the residual bone height is too thin, then the implants are inserted in a second procedure approximately 6-8 months after the sinus lift (two-time sinus lift).
A more recent method is the so-called crestal sinus lift which does not require opening a flap in a bone plate. Access to the maxillary antrum is enabled from the jaw ridge. The mucous membrane is hereby punched in the toothless region of the jaw ridge with a specifically provided punch (Jesch-Punch) and a blind hole is milled into the bone with a cylindrical milling tool, terminating just below the sinus mucous membrane. The employed punch automatically lifts the mucous membrane disk from the bone and produces a central punch mark for the additional bore (milling). The bore is typically milled antrally (from the ridge) with a cylindrical milling tool (for example with a diameter of 3.5 mm) to about 1 mm below the bonelike floor of the maxillary antrum, wherein the bone thickness is measured in advance using x-rays. Because the sinus mucous membrane must not be damaged by the milling tool, the jawbone must not be fully drilled through with the milling tool, leaving instead a thin bone plate on the floor of the blind hole, with the sinus mucous membrane abutting the backside of the bone plate.
Conventionally, this thin bone plate is then carefully pushed towards the maxillary antrum with a cylindrical instrument, whereby it is pressed towards the maxillary antrum together with the sinus mucous membrane which adheres to it above the bone disk. This “punch through” of the bone disk represents a critical point in the procedure because, if the bone disk is punched too strongly, the sinus mucous membrane is lifted like a tent and tensioned, which may lead to damage. The sinus mucous membrane is then carefully lifted, whereafter the bone replacement material is introduced through the bore into the newly created free space. The implant is then generally anchored directly in the bore.
Although very advanced methods have been developed for detaching the sinus mucous membrane through the small bore (which mostly has a diameter of only approximately 4 mm) in a very gentle manner and sufficiently away from the jawbone, a critical moment remains when the jawbone is punched through, demanding significant experience and particular skill from the physician, so that in spite of the careful attention there remains a residual risk that the sinus mucous membrane is damaged when punching through the bone plate.
To make the sinus lift procedure safer, additional tools would be desirable which would make it easier to penetratingly extend the jawbone bore while reducing the damage risk to the delicate sinus membrane behind the jawbone.